Compound leverage metal-cutting shears



COMPOUND LEVERAGE METAL-CUTTING SHEARS Filed Feb. 14, 195C rwentor:

- kosa-Rr H MecoY,

Patented Jan. 12, 1954 PATENT OFFICE COMPOUN D LEVERAGE SHEAR METAL-CUTTING S Robert H. McCoy, Salt Lake City, Utah Application February 14, 1950, Serial No. 144,111

2 Claims. 1

This invention relates to metal-working tools, and more particularly to improvements in metalcutting shears of compound leverage type.

Metal-cutting shears arranged to exert a compound leverage upon the cutting blades thereof are broadly old, various constructions having been heretofore developed for the purpose. Nevertheless, these prior constructions leave considerable latitude ior improvement.

t is a primary object of the present invention to provide an improved construction for metalcutting shears of the type concerned, wherein the compound leverage is attained positively and to best advantage.

Other important objects are:

To provide a construction that is strong, durable, and capable oi exerting more powerful compressive force on the movable cutting blade of the shear than has ordinarily been possible heretofore.

To provide a tool which is convenient to use and rapid in its cutting action.

To provide an eflicient tool producing a relatively long, clean cut with each pressure stroke of the operating handle.

To provide an arrangement whereby the cutting blades may be maintained in maximum cutting relationship at all times.

To accomplish the above relatively simply and inexpensively.

One of the outstanding features of the invention is the articulative connection between the lever arm of the operating handle and the movable blade, whereby powerful compressive force is exerted immediately above the metal to be cut, without danger of tool failure.

Another outstanding feature is the correlation between such articulative connection and a means for maintaining the movable blade in close cutting relationship with the stationary blade, whereby no twisting or bending stresses are imposed upon the articulative linkage members.

Further objects and features of the invention will become apparent from the following detailed description of the typical preferred embodiment illustrated in the accompanying drawings to exemplify practical forms of the inventive concepts here disclosed.

In the drawings:

Fig. 1 represents a side elevation of the shears in open position ready to execute a, cutting operation, a portion of the long operating handle being broken 01T for convenience of illustration;

Fig. 2, a similar view showing the shears in .Closed position following a cut;

Fig. 3, a rear elevation of the position of Fig. 1;

Fig. 4, a front elevation of the position of Fig. 2; and

Fig. 5, a fragmentary vertical section taken on the line 5-5 of Fig. 5.

Referring now to the drawings: the metalcutting shears illustrated embodies a jaw structure i0, which is normally held stationary by anchoring the mount piece II thereof in a suitable xed support, such as a tripod (not shown) The stationary jaw structure I0 includes a jaw proper I2 at its forward part, and a laterally offset mounting portion I3 rising from its rearward part and joined thereto by a transverse web I4. A mounting arm I5 extends upwardly and forwardly from the mounting portion I3 to a location spaced above the jaw proper l2. Such jaw structure Ill, comprising the component parts II, I2, I3, I4, and i5, is conveniently integrally formed of mild steel by forging.

A stationary cutting blade I6 of tool steel is removably secured to jaw proper I2, as by means of screws Il.

Arranged for shearing action relative to the stationary jaw I2 is a movable jaw I8, the same being pivoted at its rearward end to the mounting portion I3, as by means of pivot screw I9, so as to work within the offset 20. A cutting blade 2l is carried by the movable jaw I8, at the forward part thereof, for cooperation with stationary cutting blade I6.

The entire movable jaw I8 is conveniently made of tool steel, and the blade 2l formed integrally therewith, as shown.

Compound leverage, operating mechanism is provided for working the movable jaw i8 relative to the stationary jaw I2, so that the two blades 2l and I6, respectively, will exert shearing action on metal to be cut by the device.

In accordance with the invention such operating mechanism comprises a strut interposed between the movable jaw and a lever arm portion of an operating handle.

In the illustrated embodiment, a manually actuated, elongate, operating handle 22 has a` forward portion 22a pivoted to the mounting arm I5, by means of a pivot pin 23. Such handle 22 is arranged above and within the offset 2i), so as to be operable directly above the movable jaw I8. Advantageously, the movable jaw I8 and the forward portion 22a of the handle are of approximately the same thickness, in order to provide substantially equivalent transverse bearing extent for the transmission of compressive force from handle to movable jaw.

A cylindrically-formed bearing recess 24 for receiving and journalling one end 25a of a strut 25 is provided in the back of the forward portion of movable jaw i8, the same extending transversely of such jaw I8, from side-to-side thereof. Such bearing recess 24 is preferably open-ended, for a reason hereinafter made clear. A somewhat similar bearing recess 26 is provided in and at the underside of the forward portion 22a of operating handle 22 immediately to the rear of the pivot pin 23 and substantially directly above the recess 24, for receiving and journaling the opposite end 25h of strut 25, see Fig; 2. It will be noted from Fig. 2 that the recesses or openended grooves 2li and 26 are disposed immediately rearwardly of the pivot pin 23 by mutually equivalent distances.

The two ends 25a and 25h of strut 25 are cylindrically-formed to substantially correspond with the respective bearing recesses 24 and 26. For

the purpose of retaining end a of the strut Y without restricting or limiting lateral movement of movable jaw l relative thereto, the bearing recess 21's is greater than semi-cylindrical in formation. Thus, end 25a of strut 25 is inserted thereinto, or vice versa, by sliding movement toward and into an open lateral end of the recess, the recess itself providing holding means, for retaining the strut in operative position. On the other hand, to permit maximum opening movement and free action of the operating handle 22 throughout a complete shearing stroke, the bearing recess 2S is preferably made semi-cylindrical, or less than semi-cylindrical, as shown, Fig. 2. Accordingly, it is advantageous to provide e, suitable auxiliary holding means for retaining the strut 25 in operative position.

In the illustrated embodiment, the auxiliary holdingV means takes the form of a plate 21, fixed laterally to the lever arm portion 22a of the operating handle, as by means of screws'28, and pivotally secured laterally to the bearing endy or head 25h of strut 25, as by means of a pivot pin 29.

As so arranged, compressive force is exerted through strut 25, powerfully and immediately above the cutting blades, without danger of tool failure. Furthermore, an unusually effective transmission of power from handle 22, acting as a lever of the second order, is obtained by reason of the fact that the strut maintains an alignment with the direction of application of force 'by the handle at al1 times during the cutting operation (compare the positions of the strut in Figs; 1 and 2). Thus, there is no ineffective force component. Also, movable jaw IB may be quickly `and conveniently removed from the tool proper from time to time for resharpening of cutting blade 2l.

In order to insure a proper, close-cutting, working relationship between the cuttingY blades Iii and 2! at all times, even when operating upon relatively thick and tough material to be out, means are provided for preventing lateral movement of movable jaw I8 away from stationary jaw i2 beyond any given limit. Such means is preferably adjustable, and 4advantageously takes the form of a set screw 39 threaded through mounting arm I5 so as to bear against movable jaw I8 as the latter moves; see particularly Fig. 5. Such set screw 3e could, however, be threaded through movable jaw I 8, so as to bear against mounting arm l5, if found more desirable'in any given instance.

It will be noted that freedom of lateral movement of the movable jaw I3 relative to strut 25 4 insures against undue twisting stresses being im'- parted to the strut during any cutting operation. In this respect, it should be understood that a tight bearing fit of the ends of strut 25 in their respective recesses is not necessary nor desirable in most instances of use.

It should `be particularly noted that the open recess construction 26 brings the bearing point of the work arm of the leverage, upon the strut 25, close to the fulcrum 23. This provides a favorable mechanical advantage, without excessive length of the power arm 22a. Also, the direct contact between the strut ends 25a and 25h, and the surfaces of the respective bearing recesses, causes efficient power transmission and everlasting bearing action. All this is in contradistinction to ordinary pivot pin constructions customary in tools of this type.

Whereas this invention is here illustrated and described with respect to a preferred specific form thereof, it is to be understood that various changes may 'be madel therein and various other forms may be constructed on the basis of the teachings hereof, by those skilled in thev art, without departing from the protective scope of the following claims.

I claim:

l. lvfetal-cutting shears, comprising a normally stationary jaw structure; a blade carried by the forward portion of said jaw structure in Xed relationship` thereto, said jaw structure having a laterally off-set mounting portion disposed rearwardly of the blade; a mounting arm fixed to said offset mounting portion and extending forwardly therefrom to a location spaced above and at substantially the forward end of the blade; an elongate movable jaw pivoted at one end to said offset mounting portion and extending forwardly substantially coextensively with the blade and the forward extension of said mounting arm and disposed with'in said laterally offset mounting portion of the stationaryl jaw structure; a blade carried by the forward portion of said movable jaw in cutting relationship with the first-named blade; an elongate operating handle having one of its ends pivoted to the forward end of said mounting arm above the forward end of said movable jaw, and extending rearwardly therefrom; aV pair of transverse, substantially cylindrically-formed, open-ended grooves recessed into opposing faces of` the' said operating handle and the said movable jaw, respectively, andA extending from side-to-sidev thereof, said grooves being disposed substantially the same distance rea-rwardly of but closely adjacent the pivotal connection of the operating handle tothemounting arm; a strut interposed between said' operatingy handle-andsaid movable' jaw, as a powertransmitting, articulativelink, said strut having opposite ends substantially cylindrically formed and articulatively inset into said grooves ofV the' of the operating handle and pivotally secured' to the adjacent end of said strut, laterallyv of said operating handlesandfA saidV strut, the opposite end of said strut-remaining laterally free, permitting, substantially free lateral movement for said movable jaw relative" to saidy strut, and wherein there is provided a set screw operable between said mounting arm and said movable jaw for adjusting the shearing relationship of the cutting Number blades. 683,553 ROBERT H. MCCOY. 1,447,483 1,533,479 References Cited in the le of this patent 5 2,207,222

UNITED STATES PATENTS 2,375,364

Number Name Date 146,942 Nunan Jan. 27, 1874 Number 179,480 Ketterman July 4, 1876 6,082 216,078 Bean June 3, m79 10 111,816 235,416 Davies Dec. 14, 1880 Name Date Carter Oct. 1, 1901 Pazas Mar. 6, 1923 Sttt Apr. 14, 1925 McGary July 9, 1940 Hood May 8, 1945 FOREIGN PATENTS Country Date Great Britain Dec. 20, 1882 Austria Dec. 27, 1928 

